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-rw-r--r--src/util/serfloat.cpp64
1 files changed, 64 insertions, 0 deletions
diff --git a/src/util/serfloat.cpp b/src/util/serfloat.cpp
new file mode 100644
index 0000000000..8edca924cd
--- /dev/null
+++ b/src/util/serfloat.cpp
@@ -0,0 +1,64 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <util/serfloat.h>
+
+#include <cmath>
+#include <limits>
+
+double DecodeDouble(uint64_t v) noexcept {
+ static constexpr double NANVAL = std::numeric_limits<double>::quiet_NaN();
+ static constexpr double INFVAL = std::numeric_limits<double>::infinity();
+ double sign = 1.0;
+ if (v & 0x8000000000000000) {
+ sign = -1.0;
+ v ^= 0x8000000000000000;
+ }
+ // Zero
+ if (v == 0) return copysign(0.0, sign);
+ // Infinity
+ if (v == 0x7ff0000000000000) return copysign(INFVAL, sign);
+ // Other numbers
+ int exp = (v & 0x7FF0000000000000) >> 52;
+ uint64_t man = v & 0xFFFFFFFFFFFFF;
+ if (exp == 2047) {
+ // NaN
+ return NANVAL;
+ } else if (exp == 0) {
+ // Subnormal
+ return copysign(ldexp((double)man, -1074), sign);
+ } else {
+ // Normal
+ return copysign(ldexp((double)(man + 0x10000000000000), -1075 + exp), sign);
+ }
+}
+
+uint64_t EncodeDouble(double f) noexcept {
+ int cls = std::fpclassify(f);
+ uint64_t sign = 0;
+ if (copysign(1.0, f) == -1.0) {
+ f = -f;
+ sign = 0x8000000000000000;
+ }
+ // Zero
+ if (cls == FP_ZERO) return sign;
+ // Infinity
+ if (cls == FP_INFINITE) return sign | 0x7ff0000000000000;
+ // NaN
+ if (cls == FP_NAN) return 0x7ff8000000000000;
+ // Other numbers
+ int exp;
+ uint64_t man = std::round(std::frexp(f, &exp) * 9007199254740992.0);
+ if (exp < -1021) {
+ // Too small to represent, encode 0
+ if (exp < -1084) return sign;
+ // Subnormal numbers
+ return sign | (man >> (-1021 - exp));
+ } else {
+ // Too big to represent, encode infinity
+ if (exp > 1024) return sign | 0x7ff0000000000000;
+ // Normal numbers
+ return sign | (((uint64_t)(1022 + exp)) << 52) | (man & 0xFFFFFFFFFFFFF);
+ }
+}